Processing kodak motion picture films, module 3 analytical procedures

Thiosulfate (Hypo)
Sample Treatment
1. Pipet 3.00 mL of sample into a 250-mL conical flask.
2. Add 5 mL of 37.5 percent formaldehyde solution from
a tip-up pipet.
3. Add three to four drops of phenolphthalein indicator.
a. If the solution is pink, titrate with 1.0 N sulfuric
acid to colorless.
b. If the solution is colorless, titrate with 1.0 N
sodium hydroxide to the first light pink color.
4. Let the solution stand for two minutes.
5. Add 10 mL of 2.0 N acetic acid from a tip-up pipet.
6. Add 5 mL of 50 g/L zinc sulfate from a tip-up pipet.
Titration
1. Add, from a tip-up pipet, 5 mL of starch indicator to
the sample.
2. Titrate with standarized 0.1N iodine to the first distinct
blue color.
Calculations:
1. Sodium Thiosulfate:
Na 2 S 2 O 3 5 H 2 O, g/L =
(N I 2 )(mL I 2 )(eq wt (Na 2 S 2 O 3 5H 2 O)(1000)
(mL sample)(1000)
(N I 2)(mL I 2)(248.19)(1000)
82.73 (N I 2 )(mL I 2 )
(3.00)(1000)
2. Ammonium Thiosulfate:
(NH 4 ) 2 S 2 O 3 [58.6%], mL/L * =
* The average of nine typical lots of ammonium thiosulfate stock
solution tested was 58.6% as ammonium thiosulfate and
contained 0.7% as ammonium sulfite, the sp gr = 0.5688.
(N I2 )(mL I2 )[eq wt (NH4 ) 2S2O3 ](103)(102) (mL sample)[%(NH 4) 2S 2O 3][sp gr (NH 4) 2S 2O 3](10 3)
(N I 2 )(mL I 2 )[63.8](1000)(100)
(3.00)[58.6][0.5688](1000)
63.8 (N I 2 )(mL I 2 )
=
=
=
=
Bisulfate and Sulfite (as Na 2 SO 3 )
Na 2 S 2 O 3 , g/L = 2.10 [(H.I.) – (mL I 2 for hypo)]
Table 1 Reducing Capacity of Fixer Constituents
(mL of standardized 0.1 N Iodine Consumed by
1.00 g or mL of Constituent)
Constituent Theoretical By Experiment
Ammonium thiosulfate
solution, mL
53.1 53.5 *
Sodium sulfite, g 159 156 †
Sodium bisulfite, g 192 207 ‡
Sodium thiosulfate 40.3 40.3 §
* Using a sample of solution having an assay of 58.5 percent and
containing 0.86 percent ammonium sulfite (ANSI PH4.252-1987).
Ammonium thiosulfate and ammonium sulfite contributed to theoretical
value to the extent of 52.1 and 0.98 respectively, and to the
experimental value by 52.1 and 1.4 respectively.
† Using photographic grade sodium sulfite which has a minimum assay
of 97.0 percent as sodium sulfite (ANSI PH4.275-1987).
‡ Using sodium bisulfite which assayed 107.5 percent as sodium
bisulfite (ANSI PH4.276-1987).
§ Using photographic-grade sodium thiosulfate crystalline which has an
assay between 99.0 and 101.0 percent as sodium thiosulfate
pentahydrate (ANSI PH4.250-1987
Table 2 Contribution of Constituents to Hypo
Index of a Process ECP-2 Fixer
Replenisher Constituent Mix Value
Fresh Ammonium
thiosulfate *
* 58.6 Percent solution.
mL 0.1 N I 2
Consumed
Theoretical
170.0 mL 27.1
Sodium sulfite 16.0 g 7.6
Sodium bisulfite 5.8 g
(3 mL sample)
2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03
3.3
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